Conteol op electbical enebgy



Aug. 27, 1929. c, A, s u 1,725,94Q

CONTROL OF ELECTRICAL ENERGY Original Filed April 1, 1918 2 Sheets-Sheet 1 d L I 5% ea =5 1 "4 65 9b 95 QBQAZS 3 5.

57 i T 67 r r lm emor:

Aug. 27, 1929. c. A. SPRAGUE 1,725,940

CONTROL OF ELECTRICAL ENERGY Original Filed April 1, 1918 2 Shgets-Sheet 2 Patented Aug. 27, 1929 UNITED STATES PATENT OFFICE.

CLARENCE SPRAGUE, OF EAST ORANGE, NEW JERSEY, ASSIGNOR TO RADIO CORPORATION OF AMERICA, A CORPORATION OF DELAWARE.

CONTROL OF ELECTRICAL ENERGY.

Original application filed April 1, 1918, Serial No. 226,127. Patent No. 1,595,429, dated August 10, 1926. Divided and thisapplication filed May 15, 1926, Serial No. 109,330. Renewed May 19, 1928.

This invention relates to a method of and means for quantitatively controlling'large amounts of energy for any desired purpose through the use of a small controlling force.

It often becomes desirable to produce a large periodic force having a period the same as that of a given smaller force, as for example in the reproduction of an amplified sound wave or etheric or electronic wave. To do this it becomes necessary to provide a relatively large supply of energy and to periodically transform or direct portions of this energy at the desired rate, or to bring a large force into play in such a manner as to produce the desired form of energy at the desired rate. It is difiicult to do this automatically by means of a relatively small controlling force such as that of a sound wave to be amplified. One of the objects of this invention is to provide a method of and means for accomplishing this in such a manner as to produce much greater amplification than that ordinarily obtained. In

the known methods of amplification it is often necessary to perform the process in several. stages before the desired degree of amplification is obtained. By my invention a large amplification may be obtained in a single stage. Other objects of the invention will appear from the following description and appended claims.

In accordance with my invention electricity is set in motion and controlled by a device in the nature of a gate-valve which in turn is controlled by the relatively small amounts of energy obtained from the force or wave to be amplified or reproduced, and the force exerted by the moving electricity upon the valve device, or the charge thereon, is removed or greatly reduced at intervals to permit the valve to be repeatedly reset and locked.

My invention will be better understood by reference to the accompanying drawings in which:

Figures 1, 2, 3, 4, and 5 are diagrammatic views of different forms of electrical reproducing or amplifying systems according to my invention.

Referring to Fig. 1, the speech or sound [0 be reproduced or intensified impinges upon the diaphragm of the transmitter I. The current from the battery 4 in the transmitter circuit is thus varied in accordance with the sound Waves and these variations induce an alternating current of similar characteristics in the secondary circuit of the transformer 2, 3. The current through the secondary 3 oscillates between the condenser 5 and the grid 11 of the vacuum gatevalve device 10. A very small spark gap 9 is inserted in the circuit between the secondary 3 and the grid 11. Adjacent thi spark gap is an ultra violet light source .shown in the drawings as a mercury vapor rectifier 16, having the side branch circuit 17, which maintains the lower end of the mercury column in the tube conductive. To render the tube a positive rectifier it may be necessary to provide cooling means for the upper portion of the tube. The purpose of this ultra-violet light source is to periodically ionize the spark gap 9. Also adjacent the spark gap 9 is a blow-out coil 15, the purpose of which is to periodically render the spark gap 9 non-conducting. The coil 15 and the light source 16 are connected in shunt with each other and with the induc-- tance coil 18 of the main oscillatory circuit II.

Instead of providing a continuous currentwhose energy is to be controlled by the energy of the speech currents, I employ an oscillating current of relatively high frequency. This current flows in the circuit II. The oscillations are induced by means of the transformer 22, 23, the primary of which is connected to a source of oscillations of the desired frequency. The source of oscillations is shown in the drawing as a uenched spark gap circuit III containing t e rectifying device 24 and the spark-gap device 25. Any other known source of oscillating currents may, however, be employed.

The circuit II may be tuned to the frequency desired (preferably that of the source of oscillations III) by means of the variable inductance 18 and the variable condenser 21. The variable impedance 19 may be placed in the circuit II in shunt to the valve device 10, if desired, by means of switches 26 and 27.

The gate-valve device 10 consists of an evacuated container for the grid 11 and the heated filaments 12 and 13. The grid and filaments are similar to those employed in the vacuum tube device known as the audion,

the filaments being maintained in a heated condition bymeans of the battery 28 in the well known manner. This gate-valve device is conducting in both directions, its conductivity depending upon the electrical condition of the grid 11. For the purpose of this invention the vacuum of the device and the other vacuum devices shown in the drawing may vary within wide limits. It may be so high that the discharge will be entirely electronic or it may, on the other hand, approach atmospheric pressure if means are provided to prevent disintegration of the heated filaments and the charge on the grid is prevented from changing due to current therefrom or thereto within the vacuum device. In case a discharge is employed which is entirely electronic, negative biasing of the vacuum tube can be relied upon to prevent such current flow, this being the only means herein disclosed; but the invention in its broad aspects is not limited to the particular means described.

The rectifier 14 is placed in series with the blow-out coil 15 for a purpose which will later appear.

.The receiving circuit IV is shunted around the condenser 21. It consists of a condenser 20, the rectifying device 8 and the telephone receiver 7'.

A battery 29 of any desired voltage may be connected around the condenser 5 by means of the switch 31. The function of this battery is to place a negative charge upon the grid circuit.

A relatively high variable resistance 30 may be connected to the circuit of grid 1.1 by means of switch 82. It may be necessary to employ this resistance to permit a leakage regulation of what might otherwise be an excessive charge upon the grid 11.

The operation of the system shown in Fig. 1 is as follows. A frequency of oscillation is chosen for circuit 11 which is much greator than the frequency of the sound wave to be reproduced and is preferably, thonot necessarily, above the upper limit of audibility. The impedence of the gate-valve 10 being relatively high, the circuit II may not be a very persistent oscillator. In such case the circuit II should receive an impulse during each period. This impulse may be in either direction but is preferably that indicated by the position of the rectifying de vice 24-, which will induce a current in the circuit IT. in the direction of the arrow. If

the circuit 11 is a persistant oscillator the out coil 15. Assuming for convenience that current in the circuits flows from negative to positive, this being the direction in which an electronic discharge appears to take place across an evacuated space or gap in the circuit such as the gap within the space discharge device 10, current will flow from the left end of coil 18 to the rectifier 14 and blow-out coil 15 back to the circuit 11. No current will flow through the lamp 16, which is' conductive only in the reverse direction. The blow-out coil 15 will instantly render the gap 9 non-conducting.

When the current in the circuit is in the opposite direction to that indicated by the arrow, the drop in potential across the coil 18 will cause a current to flow through the lamp 16 but can not produce a current through the blow-out coil 15 because of the rectifier 14-.

- It is seen therefore that the gap is rendered alternately conducting and non-conducting by the current in the circuit 11.

The impedance of the valve device 10 varies with the charge upon the grid 11. The grid is preferably maintained negatively charged by means of battery 29. During operation of transmitter T, the negative charge upon the grid 11 will rise and fall in accordance with the variations in the speech waves.

Assui'ning that the current in the main circuit H is at zero value, and about to begin to fiow in the direction opposite to that indicated by the arrow, the gap 9 is non-conducting and there is a certain negative charge upon the grid 11. As soon as the current begins to flow lamp 16 will be lighted thus rendering the spark gap 9 conducting. There follows an immediate readjustment of the charge upon the grid 11. Since there is always a tendency for the charge on the grid to be varied by increasing or decreasing of the current flowing through the vulva and by changes in the charge upon the other elements within the evacuated space, as the current increases from the Zero value to the maximum value in circuit H, the negative charge upon the grid tends to decrease and will do so unless the electromotive force in coil 3 happens to be sufiiciently great and in the right direction to prevent. As the current falls to zero again, its effect upon the grid charge likewise falls to zero. This rise and fall of current in circuit H has had no effect upon the receiver 7, the current being in such direction that it could not pass through the rectifier 8.

The succeeding half wave of current in the circuit H is the effective or working portion of the current. It is in such direction as to pass through the rectifier 8 and operate the receiver 7 As the current begins to rise the charge upon the grid is subshintially the same as though the grid were removed from the valve 10. At this instant the blow-out coil becomes operative and the charge upon the grid is therefore trapped and remains so until the current in the main circuit again reverses. This will be for a very brief time as compared with the period of the voice currents.

The relatively small amounts of energy which are present in the grid circuit are thus enabled to control the large amount of energy of the current of the main circuit II.

Assuming, for example, that the frequency of the sound wave is 500 and that of the oscillating currents 25,000 there will be fifty readjustments of the charge upon the grid during the period of a sound wave. The effective half waves of the current in the circuit II are therefore varied in amplitude in accordance with the sound waves. The current through the receiver 7 will cause the reproduction of the original sound waves but with greatly increased volume.

The function of the condenser 20 is to partly smooth out the high frequency variations in the rectified current without affect ing the characteristic of the amplitude variations.

The rectifier 33 may be inserted in shunt to the valve device 10 if desired. The impedance of this rectifier may be very small compared with that of the device 10, so that the effect will be to substantially short circuit the valve 10 during the non-effective parts of the main current wave.

The principle of operation of the system shown in Fig. 2 is, in the main, the same as that of Fig. 1. In place of the microphone circuit I of Fig. 1 a receiving antenna is shown. This is inductively connected to the grid circuit which extends from the ground 57 to the grid 35. A battery 52 may be inserted in this circuit by 0 ening the switch 53 and closing the switc 54. A coil of high resistance such as that shown at 30, Fig. 1, may be connected between the grid and ground if desired.

The spark-gap 49 is inclosed in a vessel which may contain air, or other gas, at any desired pressure. The blow-out coil 47 causes the ionized gas to be brought in con tact with tube 51, which is of non-conducting material and through which a cooling fluid is circulated. The ionized gas is thus deionized. Ionization of the spark-gap 49 is produced by means of the ultra-violet light from the spark gap 45. This light is focussed upon the gap 49 by the mirror 46. The vessel 50 must be of a material which is transparent to ultra-violet light or must have a window of such material.

In this modification the blow-out coil and light source are in shunt to the condenser 42 and are in series respectively with the rectifiers 43 and 44.

The ate-valve device 34 is in this figure represented as a mercury vapor tube having mercury electrodes 37 and 38 and side-branch circuits 39 and 40. The lower flattened wall of the mid-portion of the tube is in contact with a cooling fluid in the receptacle 36. The grid 35 consists of one or more semicircular grid elements having the lower straight side parallel to the flattened. lower wall of the mid-portion of the tube 34.

The electronic or are stream through the tube 34 will not only be impeded by passage through the grid 35 but will be deflected downward thereby and into contact with more or less of the cool tube surface.

The receiving circuit IV is the same as that of Fig. 1 except that it is connected to the circuit II through a transformer 55.

A variable inductance coil 41 is included in the circuit II.

In Fig. 3 is shown a modification in which a valve tube 67 of the audion type is substituted for the tube 10 of Fig. 1 and in which the current in the main circuit II periodically falls to zero but does not reverse.

In place of the spark gap 9 of Fig. 1 with the associated blow-out coil and source of ultra-violet light a double audion-type tube is used. This consists of filaments 61 and 64, plates 62 and 63 and grid 65. The grid 89 of the valve 67 may be connected to elements 61 and 62 of tube 60. Elements 62 and 64 of this tube are connected to the plate of the tube 67 through the antenna transformer.

The grid 65 of tubes 60 is connected to the plate of the valve 66 and also by conductor 94 to the potentiometer 96 receiving current from battery 95.

The double tube 60 should be small, of low impedance when the charge on the grid is such that its impedance effect is a minimum, and" of ver small capacity.

The grid; of the tubes 66 and 67 may be connected to earth or to a positive source of potential through a high resistance to permit the leakage of an accumulating charge, in the well known manner.

66 is a second tube of the audion type, the function of which is to periodica ly reduce the current strength in the circuit II to zero value. This tube 66 is normally in series with the tube 67 in the circuit II. It will be understood that the function of the tube 67 is to change the impedance of the circuit II in accordance with the voice currents of the antenna circuit.

The circuit II is a divided circuit and inductance 81 and condensers 69, 70, 76 and 90 may be cut into or out of circuit as desired by means of switches 82, 71, 72, 73, 74, 75, 77, 92 and 93. Inductances 91 and 34 and battery 80 are permanently in circuit. Switches 86 and 87 enable the tube 67 to be cut out of circuit, in wnich case the tube 66 may also perform the function of tube 67. In

such case switches 83 and 68 are thrown to connect the tube 60 to the grid of the tube 66. The return circuit of tube 60 may terminate in the plate of tube 67 or may be connected to ground 85 by means of switch 88. The latter connection is preferred.

The operation of this system is similar to that of Fig. l and may be described as follows. Initially current from battery flowing towards coils 81 and 91 divides, part returning to the battery through the coil 81, tube 66, tube 67 and transformer 79. The other part of the current flows through coil 91, the branches containing condenser 76 and inductance 84 and condenser 69, respectively, the condenser 70 to the grid of the tube 66. This part of the current flows only momentarily, as it is merely condenser charging current. By a proper adjustment of the variable inductances and capacities, a reaction may be set up by which the current flowing into the grid of the tube 66 completely stops the flow of current through this tube, an oscillation in the circuit 84, 69, 76 immediately following whereby the charge is withdrawn from the grid and the current again flows through the tube 66. Thus oscillations are set up and maintained.

The function of the double audion 60 is to render the receiving circuit 89, 60, 88 conducting at the instant that the current through the tube 66 falls to zero. By conducting I mean conducting to the same degree as tho the double grid 65 were removed from the double audion 60. To establish this condition it is necessary to bring the twin grids 65 to a certain low potential which must be determined by trial. The grid 65 is covered with a thin layer of insulation to prevent leakage of current from the receiving circuit. If this grid were charged positively there would be an accumulation of negative charge upon the outside of the insulation. This condenser effect may be diminished or overcome by making the grid slightly negative. This may be done by adjustment of the potentiometer during operation of the system until the minimum effect is obtained in the telephone receiver.

V] hen the current in the circuit IT begins to flow again, the charge upon the grid 65 immediately changes to a value which will render the tube 60 non-conducting, thus trapping upon the grid 89 any charge which happens to be there at the instant. Incidentally, the increase in negative charge thus produced upon the grids 65 will induce a charge upon the grid 89, owing to the unavoidable eflect between the grid 65 and plate 63. However, any elfect which is thus produced upon the current through the transformer 79 will be in the direction of in creasing the amplifying power of the control system since an increase of charge upon grid 89 causes an increase in charge upon grid 65. This reaction may even be sutlicient to stop the flow of current through the valve 67 whereby this current will be interrupted at intervals between the interruptions produced by the valve 66. If this effect is found to be undesirable it may be eliminated by decreasing the size of the plate 62 or by introducin resistance in the circuit of the grids 65. No such effect will occur if the tube 67 is short circuited and the switches 68 and 83 are thrown to connect the grid of the tube 66 with the plate 62.

It will be understood of course, that the interruptions of the current in the circuit TI caused by the tube 66 mustbe of very high frequency compared with the frequency of the current in the receiving circuit. The surges of current through the transformer 79 will vary in amplitude according to the form of the current in the receiving circuit and the telephone receiver will reproduce the original sound with greatly increased intensity.

Fig. 4 is the same as Fig. 1 with the ex ception that a valve 100 of the audion type is substituted for the tube 10 of Fig. l, a plate 120 taking the place of the filament 12 of tube 10; the valve device 33 carrying the current when it is in a direction not to pass through the tube 100. Tube 33 substantially short-circuits the valve 10 during the noneifective parts of the main current wave, when the impedance of the device 33 is very small compared with that of the device 100, at it may be.

Fig. 5 is a modification of the system of Fig. 3 in which the conductivity of tubes 60 is controlled electromagnetically by means of coil 150 in a circuit inductively associated with the circuit IT through transformer 180 which is so designed with respect to the rest of the circuit that the tubes 60 are normally conducting but are rendered non-conducting whenever current starts to flow in circuit 11, that is, whenever the current rises to a value which makes the field of the coil 150 eil'ective. in this way the tube 60 locks the charge on the grid 89 (or the grid of tube 66 if tube 67 is cut out of circuit) during the mid portion at least of each current impulsein circuit 11.

Ionization rather than a purely electronic stream is relied upon to conduct the current through the tube 60, and deionizing means in the form of a cooling tube 51, as in Fig. 2, is placed in each part of the tube 60 where the ionizedgas will be forced against it by the magnetic field. Or, in place of the cooling tube, a small metallic conductor could be employed as the deionizing means, this being placed at a sufficiently great distance from the electrodes to avoid affecting the normal conductivity of the tube.

Since the current in circuit H falls to zero value periodically but does not reverse, the voltage induced in the secondary of the transformer 180 by the primary is first in one direction and then in the reverse direction for each pulse of current in the primary. The electric constants of the secondary circuit including the blow-out coil of course affect the form and time of occurrence of the secondary pulses in well known manner, so that the effective field set up by the blow-out coil may be made to occur during the mid portion at least of the period of current flow in circuit II and a period of conductivity of tube 60 during a part at least of the period of no current flow in circuit II, thus approaching at least the condition of having the corresponding periods exactly coincide.

There are many combinations both of elements and method steps which I have described above which are features of my invention and which are pointed out in the claims. With respect to these features my invention is not limited to reproducing systems. V

This application is a division of my copending application, Serial No. 226,127, filed Apr. 1, 1918, Patent No. 1,595,429, patented August 10, 1926.

I claim:

1. The combination with an oscillatory circuit, of a space discharge device having an anode, a cathode and an impedance control element, a source of potential for causing a space current to flow between said cathode and said anode, and means associating said oscillatory circuit with said device to cause the impedance of the latter to periodically vary at a frequency dependent upon the frequency of said circuit, and a second space discharge device having an anode, a cathode, and an impedance control element, said space discharge devices being in series with each other with respect to said source.

2. The combination with an oscillatory circuit, of a space discharge device having an anode, a cathode and an impedance control element, a source of potential for causing a space current to flow between said cathode and said anode, means associating said oscillatory circuit with said device to cause the impedance of the latter to periodically vary at a frequency dependent upon the frequency of said circuit, a second space discharge device having an anode, a cathode and an impedance control element, said devices being in series with each other with respect to said source, a second source of variable potential and means associating said last mentioned source with the impedance control element of said second space discharge device.

The combination with an oscillatory circuit, of a space discharge device having an anode, a cathode and an impedance control element, a source of potential for causing a space current to flow between said cathode and said anode, means associating said circuit with said device to cause the impedance of the latter to periodically vary at a frequency dependent upon the frequency of said circuit, a second source of electromotive force, means connecting said second source with said impedance control element, a variable impedance element in said connecting means, andmeans causing the impedance of said variable impedance element to vary in synchronism with the current variations periodically produced by said device in combination with said circuit.

In witness whereof, I hereunto subscribe my name this 1 1th day of May, A. D. 1926.

CLARENCE A. SPRAGUE. 

